This invention is generally concerned with a collimator for removing unwanted divergent beams of radiation received from a source, leaving a well resolved radiation beam for detection and analysis. More particularly, the invention is directed to a collimator having a layered structure for removing not only unwanted angularly divergent radiation beams, but also for removing radiation inelastically scattered by the collimator structure itself.
Radiographic imaging methods and apparatus are undergoing rapid evolution as efforts are being made to improve the ability to image selected portions of a specimen or diffract and sense radiation from the specimen. The effectiveness of these various methodologies and even the ability to use certain techniques depends primarily on spatial resolution and on the associated signal to noise ratio in the data being accumulated. Present technology is able to generate a radiation intensity adequate to image and evaluate structure and analyze a number of abnormalities. However, current technology cannot effectively collimate this radiation intensity without counting certain divergent radiation and thus including substantial unwanted noise in the resulting data. Such divergent, unwanted signal derives, for example, from radiation which has been inelastically scattered from the collimator structure itself. This deficiency therefore requires exposing the specimen to larger intensities of radiation in order to achieve a desired resolution. Unfortunately, such increased radiation exposure can be hazardous, and moreover there are some divergent radiation sources whose deleterious effects cannot be alleviated even by increasing the radiation signal level.
It is therefore an object of the invention to provide an improved method of manufacture and method for collimation of radiation.
It is another object of the invention to provide a new method of manufacture of a collimator for a radiation beam.
It is a further object of the invention to provide an improved collimating device for removing divergent radiation beams received from, or passed through, a specimen undergoing diagnostic analysis.
It is an additional object of the invention to provide a new radiation collimator assembly for providing highly resolved, high intensity data characteristic of a specimen but without having to increase exposure to radiation.
It is yet another object of the invention to provide an improved radiation collimator assembly having a layered wall material structure for substantially reducing inelastic scattered radiation present in the detected data signal.
It is still a further object of the invention to provide a new collimator having a lead base structure with an outer layer of a material which preferentially absorbs a X-rays generated from inelastic scattering of gamma rays from the lead base collimator structure.
It is yet an additional object of the invention to provide a radiation collimator having a selectable collimator length using a stack of different predetermined height collimator units.
It is still a further object of the invention to provide a gamma ray collimator of lead with a thin tin layer on the collimator walls to absorb lead X-rays generated by inelastic gamma ray scattering from the lead collimator.
Other objects, features and advantages of the present invention will be readily apparent from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings described below wherein like elements have like numerals throughout the several views.